US4671802A - Chemical enhanced fuel peat dewatering - Google Patents
Chemical enhanced fuel peat dewatering Download PDFInfo
- Publication number
- US4671802A US4671802A US06/849,769 US84976986A US4671802A US 4671802 A US4671802 A US 4671802A US 84976986 A US84976986 A US 84976986A US 4671802 A US4671802 A US 4671802A
- Authority
- US
- United States
- Prior art keywords
- peat
- dewatering
- improved process
- process according
- polyelectrolyte
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000003415 peat Substances 0.000 title claims abstract description 46
- 239000000126 substance Substances 0.000 title claims abstract description 16
- 239000000446 fuel Substances 0.000 title description 2
- 229920000867 polyelectrolyte Polymers 0.000 claims abstract description 22
- 238000000034 method Methods 0.000 claims abstract description 16
- 125000002091 cationic group Chemical group 0.000 claims abstract description 9
- 239000002253 acid Substances 0.000 claims abstract description 7
- 239000002245 particle Substances 0.000 claims description 9
- 150000003839 salts Chemical class 0.000 claims description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical class [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 2
- 239000004411 aluminium Chemical class 0.000 claims description 2
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical class [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 2
- 239000011575 calcium Chemical class 0.000 claims description 2
- 229910052791 calcium Chemical class 0.000 claims description 2
- 239000003245 coal Substances 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 claims description 2
- 239000002184 metal Substances 0.000 claims description 2
- 229920002647 polyamide Polymers 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical class [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims 2
- 239000004952 Polyamide Substances 0.000 claims 1
- 150000001875 compounds Chemical class 0.000 claims 1
- 229910052742 iron Inorganic materials 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 238000010306 acid treatment Methods 0.000 description 3
- 230000008014 freezing Effects 0.000 description 3
- 238000007710 freezing Methods 0.000 description 3
- 239000000654 additive Substances 0.000 description 2
- 150000007942 carboxylates Chemical group 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000005189 flocculation Methods 0.000 description 2
- 230000016615 flocculation Effects 0.000 description 2
- 238000010257 thawing Methods 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229920001448 anionic polyelectrolyte Polymers 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 159000000014 iron salts Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10F—DRYING OR WORKING-UP OF PEAT
- C10F5/00—Drying or de-watering peat
Definitions
- peat for energy
- peat in its natural state contains about 90 wt-% water. Most of this water must be removed either mechanically or thermally; otherwise the net energy available from peat is very low.
- the moisture content of peat should be less than 50 wt-%.
- Thermal methods are very energy intensive and are usually used only after less costly methods of mechanical dewatering have been employed.
- thermal methods such as flash dryers or rotary drum dryers are today commercially available.
- the present invention relates to a process of improving the dewatering properties of peat by addition of chemicals.
- This invention is based on the discovery that the surface properties of the waterkeeping peat particles can be substantially modified by adsorption of chemical additives which eliminate the repulsive forces. A large part of the carboxylates is thus protonated by acid treatment and the remaining charges are neutralized with a cationic polyelectrolyte.
- FIG. 1 shows the relation between the pH-value and time necessary to dewater a given peat quantity to 20% dry substance
- FIG. 2 shows the relation between amount of added polyelectrolyte (polyimin) in kg per metric ton of dry peat and time according to FIG. 1,
- FIG. 3 shows the relation between temperature in degrees Celsius and time according to FIG. 1.
- the peat is treated with an acid, for example sulphuric acid, to an optimal pH-value in respect of chemical consumption and dewatering efficiency.
- the optimal pH-value is often close to or at 3 (FIG. 1).
- acid for example sulphuric acid
- a cationic polyelectrolyte is then added to bind the colloidal peat particles together to larger aggregates.
- the polyelectrolyte shall have a charge density adapted to the charge density on the peat particles and a molecular weight preferably exceeding 2000 to enable the polyelectrolyte to further neutralize and flocculate the peat particles.
- a polyelectrolyte with a lower molecular weight will solubilize in the continuous water phase in the peat structure and can therefore not create any flocculation or neutralization.
- Polyelectrolytes from the group consisting of polyimines and polyamid derivatives are most suitable according to the present invention, but many other cationic polyelectrolytes with molecular weights exceeding 2000 are useable in this invention.
- the amount of polyelectrolyte to be added is dependent on peat quality, polyelectrolyte structure and degree of pretreatment of the peat with acid. Acid treated peat will generally consume less than 2 kg polyelectrolyte per metric ton, dry peat (FIG. 2) to give the desired dewatering efficiency. This should be compared with polyelectrolyte enhanced dewatering of peat without acid treatment, where polyelectrolyte consumption is in the order of 6 kg/metric ton dry peat.
- cationic polyelectrolyte can be combined with an addition of metal salts, preferably iron salts or salts from aluminium and calcium, whereby the polyelectrolyte addition can be further minimized.
- metal salts preferably iron salts or salts from aluminium and calcium
- anionic polyelectrolytes to the peat substances such as polycarboxylic acids, can be used to improve flocculation and thereby improve dewatering efficiency.
- the peat After chemical treatment the peat should preferably be heated to as high temperature as possible (FIG. 3) before dewatering in the press system.
- the optimal temperature from an economical point of view is mainly determined by the availability of low quality hot water or steam for example from combustion of peat in the dewatering plant.
- the water is more easily removed from the peat structure during the press operation, mainly due to the fact that the colloidal particles are flocculated which prevents plugging during water transport through fine channels in the peat structure.
- centrifuges or other mechanical devices for dewatering can be used when this invention is applied.
- Yet another method to improve the dewatering efficiency of peat is a freeze treatment after the chemical treatment. This is only of interest if freezing and subsequent thawing can be realized in an economical way. Freezing can either be performed in shallow lagoons during winter season or in a continuous industrial process, where freezing and thawing can be performed all year around. For certain peat qualities, addition of coal particles or ground dry peat may further improve dewatering efficiency.
- a substantial advantage of the present invention relative to prior art additive enhanced peat dewatering is that an acid treatment of the peat in combination with cationic polyelectrolytes reduces the cost of chemicals considerably and cuts the polyelectrolyte consumption with at least 75% at comparable dewatering efficiencies.
- a further advantage is that the present invention can be combined, as indicated above, with various other methods and chemicals to improve chemical and/or physical peat dewatering.
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- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Developing Agents For Electrophotography (AREA)
- Solid Fuels And Fuel-Associated Substances (AREA)
- Fertilizers (AREA)
- Treatment Of Sludge (AREA)
Abstract
The present invention relates to an improved process of chemically enhanced peat dewatering by pretreatment of the peat substance with an acid and a cationic polyelectrolyte before mechanical dewatering.
Description
The overwhelming problem associated with utilizing peat for energy is its high moisture content. Peat in its natural state contains about 90 wt-% water. Most of this water must be removed either mechanically or thermally; otherwise the net energy available from peat is very low. To be considered as a feedstock for conversion to synthetic fuels or for direct combustion, the moisture content of peat should be less than 50 wt-%.
Methods for dewatering wet harvested peat can be grouped into two categories - thermal and mechancial. Thermal methods are very energy intensive and are usually used only after less costly methods of mechanical dewatering have been employed. Several thermal methods such as flash dryers or rotary drum dryers are today commercially available.
Belt and roll presses using mechanical forces have achieved resulting peat moisture contents to about 75 wt-%.
The present invention relates to a process of improving the dewatering properties of peat by addition of chemicals.
Recent years' development in surface chemistry on model systems with properties similar to peat have shown that the large water keeping capability mainly is correlated to the repulsive forces between parts of colloidal size (usually 10-1000 Angstrom). The repulsive forces in peat are mainly based on electrostatic forces between charged carboxylate group located on the peat particles.
This invention is based on the discovery that the surface properties of the waterkeeping peat particles can be substantially modified by adsorption of chemical additives which eliminate the repulsive forces. A large part of the carboxylates is thus protonated by acid treatment and the remaining charges are neutralized with a cationic polyelectrolyte.
Accordingly, the process has aquired the characterisation given in claim No. 1.
A more detailed explanation of the invention will be given in the following example and enclosed diagrams where;
FIG. 1 shows the relation between the pH-value and time necessary to dewater a given peat quantity to 20% dry substance,
FIG. 2 shows the relation between amount of added polyelectrolyte (polyimin) in kg per metric ton of dry peat and time according to FIG. 1,
FIG. 3 shows the relation between temperature in degrees Celsius and time according to FIG. 1.
This invention can be practised for example in the following way:
The peat is treated with an acid, for example sulphuric acid, to an optimal pH-value in respect of chemical consumption and dewatering efficiency. The optimal pH-value is often close to or at 3 (FIG. 1). By treatment with acid the negative charges on the colloidal peat particles become almost totally neutralized.
A cationic polyelectrolyte is then added to bind the colloidal peat particles together to larger aggregates. The polyelectrolyte shall have a charge density adapted to the charge density on the peat particles and a molecular weight preferably exceeding 2000 to enable the polyelectrolyte to further neutralize and flocculate the peat particles.
A polyelectrolyte with a lower molecular weight will solubilize in the continuous water phase in the peat structure and can therefore not create any flocculation or neutralization.
Polyelectrolytes from the group consisting of polyimines and polyamid derivatives are most suitable according to the present invention, but many other cationic polyelectrolytes with molecular weights exceeding 2000 are useable in this invention. The amount of polyelectrolyte to be added is dependent on peat quality, polyelectrolyte structure and degree of pretreatment of the peat with acid. Acid treated peat will generally consume less than 2 kg polyelectrolyte per metric ton, dry peat (FIG. 2) to give the desired dewatering efficiency. This should be compared with polyelectrolyte enhanced dewatering of peat without acid treatment, where polyelectrolyte consumption is in the order of 6 kg/metric ton dry peat.
The addition of cationic polyelectrolyte can be combined with an addition of metal salts, preferably iron salts or salts from aluminium and calcium, whereby the polyelectrolyte addition can be further minimized. Also addition of anionic polyelectrolytes to the peat substances such as polycarboxylic acids, can be used to improve flocculation and thereby improve dewatering efficiency.
After chemical treatment the peat should preferably be heated to as high temperature as possible (FIG. 3) before dewatering in the press system. The optimal temperature from an economical point of view is mainly determined by the availability of low quality hot water or steam for example from combustion of peat in the dewatering plant.
By the formation of aggregates according to this invention the water is more easily removed from the peat structure during the press operation, mainly due to the fact that the colloidal particles are flocculated which prevents plugging during water transport through fine channels in the peat structure.
As an alternative to mechanical pressing of the treated peat, centrifuges or other mechanical devices for dewatering can be used when this invention is applied.
Yet another method to improve the dewatering efficiency of peat is a freeze treatment after the chemical treatment. This is only of interest if freezing and subsequent thawing can be realized in an economical way. Freezing can either be performed in shallow lagoons during winter season or in a continuous industrial process, where freezing and thawing can be performed all year around. For certain peat qualities, addition of coal particles or ground dry peat may further improve dewatering efficiency.
A substantial advantage of the present invention relative to prior art additive enhanced peat dewatering is that an acid treatment of the peat in combination with cationic polyelectrolytes reduces the cost of chemicals considerably and cuts the polyelectrolyte consumption with at least 75% at comparable dewatering efficiencies. A further advantage is that the present invention can be combined, as indicated above, with various other methods and chemicals to improve chemical and/or physical peat dewatering.
Claims (7)
1. An improved process of chemical enhanced peat dewatering where the peat substance is treated with an acid and a cationic polyelectrolyte before mechanical dewatering.
2. The improved process according to claim 1 where the cationic polyelectrolyte is selected among synthetic or naturally occuring compounds, including polyimines and derivatives of polyamides.
3. The improved process according to claim 1 where the polyelectrolyte has a molecular weight exceeding 2000.
4. The improved process according to claim 1 where the addition of cationic polyelectrolyte is combined with addition of metal salts, preferably selected among salts of iron, aluminium and/or calcium.
5. The improved process according to claim 1 where addition of ground dry peat and/or pulverized coal particles is made to the chemically treated peat.
6. The improved process according to claim 1 where the chemically treated peat substance is heated before dewatering.
7. The improved process according to claim 1 where the peat is frozen before or after chemical treatment.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE8501722A SE452891B (en) | 1985-04-09 | 1985-04-09 | PROCESS FOR IMPROVING PATHWATER DRAINAGE CHARACTERISTICS OF MECHANICAL DRAINAGE |
| SE8501722 | 1985-04-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US4671802A true US4671802A (en) | 1987-06-09 |
Family
ID=20359794
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US06/849,769 Expired - Fee Related US4671802A (en) | 1985-04-09 | 1986-04-09 | Chemical enhanced fuel peat dewatering |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4671802A (en) |
| FI (1) | FI90665C (en) |
| SE (1) | SE452891B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9561489B2 (en) | 2013-03-15 | 2017-02-07 | American Peat Technology, Llc | Particulate sorption medium prepared from partially decomposed organic matter |
| US9649620B2 (en) | 2013-03-15 | 2017-05-16 | American Peat Technology, Llc | Particulate sorption medium prepared from partially decomposed organic matter |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR385015A (en) * | 1907-02-22 | 1908-04-29 | Georges Jean Leopold Pradel | Peat treatment process |
| US2146902A (en) * | 1937-08-30 | 1939-02-14 | Martin William | Method of treating peat |
-
1985
- 1985-04-09 SE SE8501722A patent/SE452891B/en not_active IP Right Cessation
-
1986
- 1986-04-08 FI FI861492A patent/FI90665C/en not_active IP Right Cessation
- 1986-04-09 US US06/849,769 patent/US4671802A/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR385015A (en) * | 1907-02-22 | 1908-04-29 | Georges Jean Leopold Pradel | Peat treatment process |
| US2146902A (en) * | 1937-08-30 | 1939-02-14 | Martin William | Method of treating peat |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9561489B2 (en) | 2013-03-15 | 2017-02-07 | American Peat Technology, Llc | Particulate sorption medium prepared from partially decomposed organic matter |
| US9649620B2 (en) | 2013-03-15 | 2017-05-16 | American Peat Technology, Llc | Particulate sorption medium prepared from partially decomposed organic matter |
Also Published As
| Publication number | Publication date |
|---|---|
| FI861492A0 (en) | 1986-04-08 |
| FI861492L (en) | 1986-10-10 |
| SE452891B (en) | 1987-12-21 |
| FI90665B (en) | 1993-11-30 |
| FI90665C (en) | 1994-03-10 |
| SE8501722L (en) | 1986-10-10 |
| SE8501722D0 (en) | 1985-04-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| AS | Assignment |
Owner name: LARS STIGSSON, MONTELINVAGEN 22, S-237 00 B J A R Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:JONSSON, BENGT;REEL/FRAME:004551/0950 Effective date: 19860404 Owner name: LARS STIGSSON, SWEDEN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:JONSSON, BENGT;REEL/FRAME:004551/0950 Effective date: 19860404 |
|
| FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY |
|
| FPAY | Fee payment |
Year of fee payment: 4 |
|
| FPAY | Fee payment |
Year of fee payment: 8 |
|
| REMI | Maintenance fee reminder mailed | ||
| LAPS | Lapse for failure to pay maintenance fees | ||
| FP | Lapsed due to failure to pay maintenance fee |
Effective date: 19990609 |
|
| STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |